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SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
3. Maintenance Computer Interface
A. General
(1) The SDU is designed to interface with the Boeing 747--400 Central Maintenance
Computer (CMC) or the Boeing 777 On--board Maintenance System (OMS), the
Airbus Central Fault Display System (CFDS), and the McDonnell Douglas CFDS in
accordance with guidelines outlined in Boeing documents D220U050 (747--400 CMC
-- release date 3 June 1991) and D243W201--1 (777 OMS -- release date 30 October
1992) and Airbus document ABD0048 issue C, all of which supersede ARINC 604 for
their respective applications.
(2) The Boeing maintenance computers (i.e., 747--400 CMC and 777 OMS) are virtually
indistinguishable to the SDU. The operations to support these two systems are very
similar and, therefore, are presented together. The operations to support the Airbus
and McDonnell Douglas maintenance computers are very similar and, therefore, are
presented together. The SDU determines the aircraft type on which the SDU is
installed, and then supports only the functionality required by that particular system.
B. Boeing 747- -400 CMC/777 OMS
(1) General
(a) The CMC and SDU communicate with each other through an ARINC 429 data
bus using ARINC 429 words.
(b) When the SDU receives the standard ground test command containing its
equipment ID and source destination identifier (SDI), the SDU responds by
setting the command word (ARINC label 350) acknowledge bit to ACK for four
seconds. The SDU initiates a system-wide functional test. As soon as possible
during the execution of the functional test, the SDU sets the SSM for ARINC
label 350 to functional test.
(2) CMC to SDU Communication -- Automatic Fault Reporting
(a) The CMC and SDU communicate with each other through an ARINC 429 data
bus using ARINC 429 words.
(b) When the SDU receives the standard ground test command containing its
equipment ID and source destination identifier (SDI), the SDU responds by
setting the command word (ARINC label 350) acknowledge bit to ACK for 4
seconds. The SDU then initiates a system-wide functional test. As soon as
possible during the execution of the functional test, the SDU sets the SSM for
ARINC label 350 to functional test.
(c) At the conclusion of the functional test, the SDU builds the fault summary words
using ARINC labels 350 thru 354 by mapping currently active failures to the
appropriate bits in the words. Once the words are built they are latched for 30
seconds, then the SDU returns to automatic fault reporting. The SDU
continuously transmits the fault summary words to the CMC at a rate of 1 to 2
Hz, with the SSM bits set to normal operation during reporting of the test results.
Honeywell International Inc. Do not copy without express permission of Honeywell.
MCS--4200/7200 Multi--Channel SATCOM System
23- -20- -35
Page 6--90
15 Jul 2006
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